file handle leaks increase fast

[intel]

file handle leaks increase fast

[windyuan]

MengJia, please check this issue.
Thanks.

[dspmeng]

commit f0f23a8 drm: enable prime buffer sharing for cl buffer and image

With above commit, two hidden issue are triggered by our use case:
V4l2 exports dma buf fd -> DrmBoData is created and get its own fd via drm_intel_bo_gem_export_to_prime() -> drm prime driver find an already exported dma buf (by v4l2), and go to a specific path.

1. RBP Linux kernel 3.10.28 has a bug inside drm_prime.c, fixed later in 3.11. With this bug, driver already allocates fd, but failed to return it to user space. so drm_intel_bo_gem_export_to_prime() always failed in our user case, and has no way to close the fd.
2. DrmBoBuffer is created for every incoming V4l2Buffer, and allocates a fd. But it didn't close the fd in destructor.

[dspmeng]

Fixed by #217 and another linux kernel patch.